What is 3Di?

3Di™ is a unique, patented sailmaking technology that allows laminated sails to approach the balanced
loadbearing and shapeholding of a rigid airfoil. In simplified technical terms, 3Di is a flexible composite
membrane built from pre-impregnated spread filament tapes applied in multiple axes and thermo-formed on
a 3D (3DL) mold.

What is a spread filament tape?

What we think of as an individual yarn or
fiber in a sail is in fact a bundle of very small
filaments, each less than the diameter of a
human hair.

A spread filament tape is an individual
filament bundle (yarn) that has been spread
out until the individual filaments lie sideby-
side, forming an ultra-thin “tape” that is
then combined with adhesive and applied to
a paper backer. Shown here is a pre-preg
carbon/UHMWPE (Spectra/Dyneema) spread
filament tape approx. 35 microns thick.

How is a 3Di sail made?

The illustration below shows how the ultra-thin spread filament tapes are arranged in layers and then thermomolded
into a sail. Each color represents a different ply (layer ) comprised of filament tape(s). The tapes can
be any length and oriented in any direction, allowing unprecedented precision in matching sail structure to
predicted loads in the sail. Note that all reinforcements in a 3Di sail (blue layers) are applied as an integral
(internal) part of the sail laminate. .

With 3Di technology, designers have such precise control over the disposition and orientation of material
within the sail, they can come far closer to achieving the holy grail of sailmaking... BALANCED RESISTANCE
TO DISTORTION IN ALL DIRECTIONS.

Balanced distortion resistance?

Sail distortion of any type — stretch,
compression, shear or shrink — has a
negative effect on sail performance. Most sails
concentrate on resisting loads in the stretch
(tension) direction. But if you also restrict
a material’s ability to compress in the nonload,
or bias direction (see illustration), you
concurrently enhance resistance to stretch in
the loaded direction. We call this “balanced
distortion resistance.” Balancing resistance
to both stretch and compression means less
change in sail shape as the boat moves
through waves and changing wind pressures.

This is why we call 3Di “airfoil technology.” It
comes closer to matching the performance
of a rigid airfoil than any other sailmaking
technology.

How are spread filament tapes made?

Spread filament tapes, the foundation of 3Di, are produced on North’s own “pregger”, a machine that spreads
yarns into an ultra-thin layer of individual filaments, coats those filaments with adhesive and adds a backer.

1. The yarns* are drawn from a creel through
bullet boards to keep them organized as they
are fed into the “pregger” unit.

*UHMWPE (Spectra/Dyneema) yarns shown

2. In the pregger, the individual yarns are
spread into a wide array of single filaments,
merged with adhesive and applied to a paper
carrier.

3. The spread filament array, adhesive and
paper backer then travel through a 10-meter
drying ramp where solvents are burned off and
fumes evacuated. At the end of the ramp, the
spread filament array is cut into thinner tape
strips, rolled up and refrigerated.

4. The spread-filament tape rolls are then
loaded into a multi-axis, computer controlled
tape head attached to a bridge gantry.

3Di tape head applies each filament tape on a specified axis and cuts it into a specified length

5. The tape head applies each filament tape*
on a specified axis and cuts it to a specified
length.

*UHMWPE (Spectra/Dyneema) tape shown

6. The different tape layers are joined on the
mold with tapered scarf-like joints to ensure
consistent sail thickness and strength. The
laminate is then pressurized using a vacuum
bag (shown) and then heat cured. Unlike any
other sail laminate, no films are used.